A Transition in Potassium Superoxide

During the study of the magnetic properties [1] of potassium superoxide, KO2, I noticed that on cooling in liquid air the substance changes from a deep orange to a light cream color. In order to see whether or not this change in color accompanies a transition from one form to another, the following experiments were carried out

The Precise Determination of Sulfates

Experimental evidences are presented to support the necessity of precipitating barium sulfate by the addition of the sulfate to barium chloride rather than in the reverse order as is usually recommended. Factors such as loss due to creeping of the precipitate, temperature and time of digestion, heating of the barium sulfate to constant weight, and others were very carefully controlled. Data are given showing the results obtained using potassium, sodium, ammonium, and hydrogen sulfates. An explanation is offered why the results are low when the usual order of precipitation (BaCl2 to the sulfate) is followed. Microphotographs of barium sulfate obtained by different methods and under varying conditions are given

Processing and Mechanical Properties of Hot-Pressed Zirconium Diboride – Zirconium Carbide Ceramics

ZrB2 was mixed with 0.5 wt% carbon and up to 10 vol% ZrC and densified by hot-pressing at 2000 °C. All compositions were \u3e 99.8% dense following hot-pressing. The dense ceramics contained 1–1.5 vol% less ZrC than the nominal ZrC addition and had between 0.5 and 1 vol% residual carbon. Grain sizes for the ZrB2 phase decreased from 10.1 µm for 2.5 vol% ZrC to 4.2 µm for 10 vol% ZrC, while the ZrC cluster size increased from 1.3 µm to 2.2 µm over the same composition range. Elastic modulus was ~505 GPa and toughness was ~2.6 MPa·m½ for all compositions. Vickers hardness increased from 14.1 to 15.3 GPa as ZrC increased from 2.5 to 10 vol%. Flexure strength increased from 395 MPa for 2.5 vol% ZrC to 615 MPa for 10 vol% ZrC. Griffith-type analysis suggests ZrB2 grain pullout from machining as the strength limiting flaw for all compositions

Pressureless Sintering of Zirconium Diboride with Carbon and Boron Carbide Nanopowder

Zirconium diboride ceramics with and without carbon and boron carbide nano powder additives were prepared by ball milling with ZrB2 grinding media and pressureless sintering. Additions of up to 1 wt% nano-B4C and 0.5 wt% C were made to the ZrB2 powder. The materials were then sintered between 1800 and 2300 °C for between 90 and 360 min in an Ar/10H2 atmosphere. After sintering at 2200 °C for 90 min, densities ranged from 88.3 to 90.7% for the ZrB2 with 0–1.0% nano-B4C addition. Carbon additions of 0.5 wt% and nano-B4C additions from 0 to 1.0 wt% resulted in densities ranging from 90.9 to 91.9% after sintering at 2100 °C for 90 min. Grain size ranged from 16.6 to 21.7 μm for ZrB2 with nano-B4C content increasing from 0 to 1.0 wt%, sintered at 2200 °C. For the ZrB2 with 0.5 wt% C, increasing the nano-B4C content from 0 to 1.0 wt% resulted in a decrease in grain size from 25.4 to 18.5 μm. The densities achieved in this study were lower than previous pressureless sintering studies of ZrB2 that used WC-6Co grinding media, presumably due to the absence of WC and Co that can also act as sintering aids

Elevated Temperature Thermal Properties of ZrB2-B4C Ceramics

The elevated temperature thermal properties of zirconium diboride ceramics containing boron carbide additions of up to 15 vol% were investigated using a combined experimental and modeling approach. The addition of B4C led to a decrease in the ZrB2 grain size from 22 µm for nominally pure ZrB2 to 5.4 µm for ZrB2 containing 15 vol% B4C. The measured room temperature thermal conductivity decreased from 93 W/m·K for nominally pure ZrB2 to 80 W/m·K for ZrB2 containing 15 vol% B4C. The thermal conductivity also decreased as temperature increased. For nominally pure ZrB2, the thermal conductivity was 67 W/m·K at 2000 °C compared to 55 W/m·K for ZrB2 containing 15 vol% B4C. A model was developed to describe the effects of grain size and the second phase additions on thermal conductivity from room temperature to 2000 °C. Differences between model predictions and measured values were less than 2 W/m·K at 25 °C for nominally pure ZrB2 and less than 6 W/m·K when 15 vol% B4C was added

Study of the single body yawed-wing aircraft concept

Areas relating to the development and improvement of the single-fuselage, yawed-wing transonic transport concept were investigated. These included: (1) developing an alternate configuration with a simplified engine installation;(2) determining a structural design speed placard that would allow the engine-airframe match for optimum airplane performance; and (3) conducting an aeroelastic stability and control analysis of the yawed-wing configuration with a flexible wing. A two-engine, single-fuselage, yawed-wing configuration was developed that achieved the Mach 1.2 design mission at 5560 km (3000 nmi) and payload of 18,140 kg (40,000 lb) with a gross weight of 217,700 kg (480,000 lb). This airplane was slightly heavier than the aft-integrated four-engine configuration that had been developed in a previous study. A modified structural design speed placard, which was determined, resulted in a 6% to 8% reduction in the gross weight of the yawed-wing configurations. The dynamic stability characteristics of the single-fuselage yawed-wing configuration were found to be very dependent on the magnitude of the pitch/roll coupling, the static longitudinal stability, and the dihedral effect

The Seven Deadly Sins of Communication Research

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74955/1/j.1460-2466.2008.00382.x.pd

Nuclear propulsion systems engineering

The Nuclear Energy for Rocket Vehicle Application (NERVA) program of the 1960`s and early 1970`s was dramatically successful, with no major failures during the entire testing program. This success was due in large part to the successful development of a systems engineering process. Systems engineering, properly implemented, involves all aspects of the system design and operation, and leads to optimization of theentire system: cost, schedule, performance, safety, reliability, function, requirements, etc. The process must be incorporated from the very first and continued to project completion. This paper will discuss major aspects of the NERVA systems engineering effort, and consider the implications for current nuclear propulsion efforts

The Portrayal of Complementary and Alternative Medicine in Mass Print Magazines Since 1980

Objectives: The objectives of this study were to examine and describe the portrayal of complementary and alternative medicine (CAM) in mass print media magazines. Design: The sample included all 37 articles found in magazines with circulation rates of greater than 1 million published in the United States and Canada from 1980 to 2005. The analysis was quantitative and qualitative and included investigation of both manifest and latent magazine story messages. Results: Manifest analysis noted that CAM was largely represented as a treatment for a patient with a medically diagnosed illness or specific symptoms. Discussions used biomedical terms such as patient rather than consumer and disease rather than wellness. Latent analysis revealed three themes: (1) CAMs were described as good but not good enough; (2) individualism and consumerism were venerated; and (3) questions of costs were raised in the context of confusion and ambivalence